Forwarding system foe



Nov; 6,1923; 1,472,849

W. H. MARTEN FORWARDING SYSTEM FOR OCEAN CABLES AND THE LIKE Filed Jun18, 1918 I k E 1N VEN TOR.

WHMamin B112 S ATTORNEY Patented Nov. 6, 1923.

UNITED STATES PATENT OFFICE.

WILLIAM H. MARTIN, OF NEW YORK,'N. TL, ASSZGNOR TO AMERICAN TELEPHONEAN.

TELEGRAPH GOLMPANY, A CORPORATION 0F NEW YORK.

FORWARDING SYSTEM FOR OCEAN CABLES AND THE LIKE.

Application filed June 18,

To all whom it may concern:

Be it known that 1, WILLIAM H. MARTIN, residing at New York, in thecounty of New York and State of New York, have invented certainImprovements in Forwarding Systems for Ocean Cables and the like, ofwhich the following is a specification.

This invention relates to transmission systems involving lines of highdistortion and attenuation, such as ocean cables, and to the operationof such lines in connection with adjoining land lines. Its object is toimprove the operation of signaling over circuits of the characterindicated and to provide an arrangement whereby signals over oceancables may be retransmitted automatically to inland lines.

As is well known, the signal impulses received over such circuits asocean cables are, because of the characteristics of the line, extremelyfaint and quite different from the transmitted impulses. They are,generally speaking, too attenuated to affect any but the most delicaterecording apparatus and cannot be used in relays for forwarding thesignals over other lines. Moreover their wave form is not suited to thispurpose.

This invention proposes to combine with ocean cables and like circuits,complete inetallic forwarding circuits designed to transmit faithfullyimpulses of relatively small amplitude compared with the usual telegraphcurrents, and to connect the two transmitting circuits byinstrumentalities designed to so improve the wave form and increase itsamplitude as to make possible the operation of relays for forwarding orrecording the messages. Means are also provided for avoidingdisturbances of the somewhat delicate system for handling the receivedimpulses, by the more pronounced impulses of outgoing messages in duplexoperation.

The invention will be described in coI1- nection with the accompanyingdrawing in which Figure 1 illustrates diagrammatically one embodimentthereof, and Fig. 2 shows a modification of one detail. The circuit 1 ofhigh distortion and attenuation, here indicated as an ocean cable, isconnected through the usual capacity ratio arms 2 and 3 with theartificial line 4 and the incoming signals are taken off at the junctionpoints 5 and 6 of the ratio arms with the main and artificial linesrespectively. The conductors 7 1918. Serial No. 240,623.

and 8 for the incoming signals lead to the correcting distortion network9 which in practice may assume a variety of forms dependingupon thecharacteristics of the cir-, cuits 3rd apparatus used. It is hereshownas comprising an inductance 10 and resistance 11 connected in seriesacross the circuit, a capacity 12 in series with the circuit which ispreferably shunted by an impedance which may comprise inductance 13 andresistance lei and a second shunt across the main circuit comprisinginductance 15 and resistance 16, portion of which latter may be shuntedby the capacity 17. The effect of this network in general is to producederivatives of the arrival current which are combined with each otherand with the arrival current itself to produce a more efiective form ofcurrent wave for recording purposes. The network itself is the inventionof another and need not be further described in detail, as it does notper se constitute a part of the present invention.

The effect of the distortion network is to improve the form of thecurrent wave at the expense of current strength, so that the alreadyattenuated signal impulses are further weakened at the output side ofthis circuit. To correct this condition the current is fed to anamplifier 18 preferably of a thermionic type by which largeamplification can be secured without substantial distortion of thecurrent wave. The current is then led to one terminal of the forwardingline 19-20, here indicated as a complete metallic circuit which has theadvantage that it is free from the disturbing effect of earthpotentials, etc, common in ordinary telegraph circuits and is operablewith comparatively weak current impulses. The signal impulses from theamplifier are applied to the center points of impedances 21 and 22, onebeing located in each side of the metallic circuit. One terminal of eachimpedance is connected to one side of the metallic circuit and the othertwo terminals of the impedances are connected to the artificial line Ndesigned to simulate the main line as is customary in repeater circuitsand the like where two-way transmission is desired. The impedances 21and 22 may conveniently constitute the windings of relays for thesending branch of the circuit as indicated in the drawin The recordingdevice 23 at 51c opposite 3 navasse end of the circuit 1920 is providedwith duplicate coils, one associated with each side of the line. As hereindicated they are connected across the terminals oi impedance elements241- and 25 which are respectively in series with the opposite sides ofthe line; and the sending branch 2627 of the duplex set is connected atthe center point 0t these impedances. The windings of the recorder 23may themselves constitute the impedance elements and the sending branchmay be connected at their center points if desired as in the case of theimpedance elements 21 and 22 which likewise constitute the windings ofthe forwarding relays. Artificial line N is connected to the oppositeends of impedances 24 and 25 for balancing the circuit 19-20 withrespect to the impulses l rom the sending branch 2G27 of the duplex set.The sending device 28 is of the typical -form used in cable transmissionhaving two separate keys or contacts for transmitting, respectively,impulses of opposite sign to the circuit. In series with the sendingbranch I have provided a device 29 for rounding off the corners of thetransmitted impulses at the sending end. The impulses at the sending keyare characterized by sudden rises in value and sharp corners at thepeak. The sudden changes of current strength indicated by the corners ofthis curve are entirely lost in transmission over circuits of the kindunder consideration, and cannot, therefore, be availed of in therecording instrument. At the same time it is difiicult to prevent theserapid changes from getting into the local receiving circuit which ismade sensitive to comparatively weak current impulses, where they have adisturbing effect. The rounding oil device 29 may conveniently consistof an inductance 30 connected in each side of the circuit with acapacity 31 connected in shunt thereto, preferably at substantially themidpoints of the inductance 30. This arrangement of elements will, inaccordance with well-known principles, have the effect of rendering lessabrupt the sudden changes in current received from the sending device.

As above indicated the impedances 21-22 may conveniently form thewindings oi torwarding relays 32 and 33, each Ol' which is a polarizedrelay having opposite cont acts connected respectively to the positiveand negative sides oil the current source 41. The tongues of theserelays are connected to the opposite sides 34- and 35 of thetransmitting branch of the duplex set for circuit 1, and perform thesame function in sending impulses of opposite sign to that line as thekeys of the instrument 28 above mentioned. The circuit 3435 is alsopreferably provided with a device 36 for rounding of the corners of theimpulses created by the relays 32 and 33, in the same manner and for thesame purpose as the device 29 above described. lnasmuch as the conductor34: is a ground connection only, it is not necessary to include theinductance elements in that side of the circuit.

The operation of the system will in the main be obvious from theforegoing. Incoming impulses from the line 1 entering the circuit 7-8will be reformed in contour by network 9 to approximate the wavetransmitted, and are amplified in the device 18, whereupon they enterthe mid-points of the impedances 21 and 22 where they will divideequally between the main line and the artificial line N ano willconsequently not affect the relays 32 and 33. Arriving at the impedances2i and 25 they will enter the windings or the device 23 and there recordthe message. Tmpulses transmitted from the sending station 28 will,after being modified by the rounding ofi device 29, enter the centerpoints 01" impedances 2i and 25, there dividing equally between the mainline and the artificial line N and accordingly will not affect thereceiving instrument 23. The impulses in the conductors l9 and 20 beingof opposite sign will oi course oppositely affect the relays 32 andThese relays both normally rest upon contacts connected to the same sideof the source 34 The impulse in one of the conductors 19--2O will be ofa polarity to throw the corresponding relay to the opposite contact andthe conductors 3d35 will accordingly be connected to the opposite sidesof the source 34, and an impulse oi": corresponding sign will betransmitted to the line 1. This impulse will have its form modified bythe device 36 in the same manner as the impulse transmitted from thestation 28, and will divide equally between the ratio arms 2 and 3 andthe main and artificial lines 1 and 4:, hence not aliecting thereceiving branch 7-8 of the duplex set. It is to be noted that thecombination oi. the correcting network and the distortionless amplifierespecially when used with the closed metallic circuit makes it possibleto forward impulses from an ocean cable or like circuit without theinterposition of mechanical relays, when desired.

In the modification shown in Fig. 2 the receiving branch of the duplexset associated with circuit 1 is to be understood as similar in allrespects to that shown in Fig 1, except that the output circuit of theamplifier 18 is used to operate relays 37 and 38 which send impulsesfrom the source 39 to the forwarding circuit 19-20, instead oftransmitting thereto the amplified impulses themselves as in Fig. 1. Inthis arrangement the windings of the relays 3738 may conveniently beconnected in series across the out put circuit of the amplifier thusreplacing the primary winding of the transformer shown in that circuitin Fig. 1. The tongues of the relays 37 and 38 are biased by anyconvenient means such as the springs indicated on the drawing, so thatin the absence of current through their windings both would lie againstthe inner contacts as shown in Fig. 2, but the strength of the springsis so proportioned to the strength of their respective windin s thatwith a normal current flowing in the output circuit of the amplifier 18one of the windings overcomes its biasing spring as shown in the relay38, whereas the other winding is not of suflicient strength to move itscontact against the pull. of the spring, as indicated in the relay 37.An increase of current above the normal due to an impulse in onedirection in the input circuit of the amplifier will cause the tongue of87 to move to the opposite contact, thus sending an impulse of onepolarity to the line, while a decrease of current below normal soweakens the winding of re lay 38 that its tongue moves under theinfluence of the spring to the opposite contact, thereby sending animpulse of the op posite sign to the line. In view of the introductionof the new source of current and the relays in this arrangement, it ispret erable to introduce a device 40 between the relays and the circuit19-2O for rounding oil the corners of the impulses as above described inconnection with the devices 29 and 36.

The invention is not to be regarded as limited to the specificarrangement herein illustrated and described, as it will be obvious tothose skilled in the art that various changes in the details may be madewithin the scope oi the invention as here disclosed and claimed.

What is claimed is:

1. In a system for transmitting signals, a transmission line of highdistortion and attenuation, a line of comparatively low distortion andattenuation, transmitting mechanism for producing impulses suitable fortransmission over said last named circuit, means at the receiving end ofsaid first named circuit for reforming received impulses, asdistinguished from regenerating them, so that they have a wave formapproximating that at the transmitting end, a distortionless amplifierfor increasing the amplitude of the reformed impulses and connecforapplying the amplified impulses i said transmitting mechanism.

2. In a system for transmitting signals, a transmission line of highdistortion and attenuation, a receiving circuit connected thereto, anetwork associated with the receiving circuit for reforming receivedcurrent impulse to a wave form approximating transmitted impulses asdistinguished the impulses, a ;thermionic amplifier having its inputcircuit connected to the reforming networir and its output circuitconnected to a balanced line of low distortion and attenuation.

3. In a system for transmitting signals, the combination with aplurality of transmission lines one of which is characterized byattenuation and distortion, of a connecting circuit comprising means forreforming signaling impulses received over the transmission linecharacterized by attenuation and distortion and a the anionic vacuumtube for amplifying the reformed impulses and for impressing the saidimpulses upon another of the said transmission lines.

4;. In a system for transmitting signals, the combination with pluralityof transmission lines one of which is characterized by attenuation anddistortion, of a connecting circuit comprising means for reformingsignaling impulses received over the transmission line characterized byattenuation and distortion, a thermionic vacuum tube for amplifying thereformed impulses and a transmitting mechanism controlled by the saidamplified impulses for impressing signaling impulses upon another of thesaid transmission lines.

5. In a system for transmitting signals, the combination with a linecircuit charac terized by attenuation and distortion, of a second linecircuit, means to impress signaling impulses on each of said linecircuits and a connecting circuit comprising a circuit to reshape thearrival wave of the first line circuit, so that it will be substantiallya reproduction of the transmitted wave and a distortionless amplifier toamplify the said reshaped wave and transmitting means controlled by theamplified wave to impress corresponding signals upon the said secondline circuit.

6. In a system for transmitting signals, the combination with a linecircuit characterized by attenuation and distortion, of a second linecircuit, both of said line circuits being adapted for duplex operation,and a connecting circuit adapted to transfer signals from the said firstto the said second line circuit comprising a wave reforming circuit anda distortionless amplifier, a second connecting circuit adapted totransfer signals from the said second to the said first line circuit andconnecting means adapted to prevent reaction between the said connectingcircuits.

In testimony whereof, I have signed my name to this specification this17th day of June, 1918.

from regenerati WILLIAM H. MARTIN.

